A conventional surface acoustic wave device disclosed in Japanese Patent Laid-Open No.3-14308 includes a piezoelectric substrate and an electrode provided on the substrate. The electrode is constructed of an epitaxially-grown aluminum film having a certain crystal orientation. The film contains a little additive, such as Cu, Ti, Ni, Mg or Pd, which has excellent migration resistance, thus preventing migration.
The electrode is formed of the single-layer epitaxially grown aluminum film and has grain size grown as large as a thickness of the film. Consequently, if having a thickness equal to or more than a certain thickness, the electrode weakens against a stress accompanied with propagation of surface acoustic waves, thus exhibiting a degraded resistance to an electric power. Particularly being constructed of a single-crystal film having no grain boundary, the electrode has a sub-grain boundary formed when the stress is applied for a long time. Consequently, the stress concentrates on the portion, thus weakening the electrode against the stress accompanied with the propagation of the surface acoustic waves.